AC coupling circuit with hybrid switches

Abstract

A coupling apparatus having a first branch and a second branch is disclosed. The first branch generally comprises (A) a first switch group configured to connect an input signal to an output node through a first capacitor, and (B) second switch group configured to connect either (i) a second signal, or (ii) a ground voltage, to the output node through a second capacitor. The second branch generally comprises (A) a third switch group configured to connect the input signal to the output node through a third capacitor, and (B) a fourth switch group configured to connect either (i) the second signal, or (ii) the ground voltage, to the output node through a fourth capacitor.

The invention claimed is: 
     
       1. A coupling apparatus comprising:
 a first branch comprising (A) one or more first switches configured to connect an input signal to an output node through a first capacitor, and (B) a plurality of second switches configured to selectively connect a second signal and a ground to said output node through one of (i) said first capacitor and (ii) a second capacitor; and 
 a second branch comprising (A) one or more third switches configured to connect said input signal to said output node through a third capacitor, and (B) a plurality of fourth switches configured to selectively connect said second signal and said ground to said output node through a fourth capacitor. 
 
     
     
       2. The apparatus according to  claim 1 , wherein said first capacitor and said third capacitor have different values. 
     
     
       3. The apparatus according to  claim 1 , wherein said third switches and said fourth switches are configured to provide a plurality of selectable attenuations to said input signal before said input signal reaches said output node. 
     
     
       4. The apparatus according to  claim 1 , wherein said third switches and said fourth switches are configured to adjust one or more of (i) an input pole of said apparatus, (ii) an attenuation of said input signal through said apparatus, and (iii) a high pass filter time constant of said apparatus. 
     
     
       5. The apparatus according to  claim 1 , wherein said apparatus adjusts a frequency of a high pass filter operation provided by said first, second, third, and fourth capacitors. 
     
     
       6. The apparatus according to  claim 1 , further comprising a resistor connected between said output node and a second output node. 
     
     
       7. The apparatus according to  claim 1 , wherein (i) said first branch positions said first capacitor between said input signal and said first switches and (ii) said second capacitor between said second switches and said output node. 
     
     
       8. The apparatus according to  claim 1 , wherein (i) said first branch positions said first capacitor between said input signal and said first switches and (ii) said second capacitor between one of said second switches and said second signal. 
     
     
       9. The apparatus according to  claim 1 , wherein said first branch positions said first capacitor between said first switches and said output node. 
     
     
       10. The apparatus according to  claim 1 , wherein said second signal comprises at least one of (i) an AC signal, (ii) a DC signal and (iii) a calibration signal. 
     
     
       11. The apparatus according to  claim 1 , wherein said one or more first switches comprises at least two of said first switches. 
     
     
       12. The apparatus according to  claim 1 , further comprising:
 a third branch connected in parallel with said first branch, wherein said third branch comprises (A) one or more fifth switches configured to connect said input signal to said output node through a fifth capacitor, and (B) a plurality of sixth switches configured to selectively connect said second signal and said ground to said output node through said fifth capacitor. 
 
     
     
       13. The apparatus according to  claim 1 , wherein said second capacitor comprises two capacitors connected to two respective ones of said second switches. 
     
     
       14. The apparatus according to  claim 1 , wherein said first branch comprises at most two capacitors. 
     
     
       15. The apparatus according to  claim 2 , wherein said second capacitor and said fourth capacitor have different values. 
     
     
       16. The apparatus according to  claim 6 , wherein said resistor and said first capacitor are configured to provide high pass filtering of said input signal. 
     
     
       17. An apparatus comprising:
 a plurality of branches connected in parallel, wherein (A) each of said branches comprises (i) one or more first switches configured to connect an input signal to an output node through a first capacitor and (ii) a plurality of second switches configured to selectively connect a second signal and a ground to said output node through one of (a) said first capacitor and (b) at least one second capacitor and (B) said second switches are configured to provide a plurality of selectable attenuations to said input signal before said input signal reaches said output node. 
 
     
     
       18. The apparatus according to  claim 17 , wherein (i) said first capacitor is positioned between said first switches and said input signal, (ii) said at least one second capacitor comprises two second capacitors, and (iii) each of said second capacitors is disposed between one of said second switches and a respective one of said second signal and said ground. 
     
     
       19. The apparatus according to  claim 17 , wherein a sum of said first capacitor and said at least one second capacitor is less than a number of said first switches. 
     
     
       20. The apparatus according to  claim 17 , wherein said apparatus is implemented as one or more integrated circuits.